This invention relates generally to magnetic disk data storage systems, and more particularly to the use of a ramp to facilitate the loading and unloading of sliders.
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In FIGS. 1A and 1B, a magnetic disk data storage system 10 of the prior art includes a sealed enclosure or housing 12, a spindle motor 14, a magnetic medium or disk 16, supported for rotation by a drive spindle S1 of the spindle motor 14, a voice-coil actuator 18 and a load beam 20 attached to an actuator spindle S2 of voice-coil actuator 18. A slider support system consists of a flexure 22 coupled at one end to the load beam 20, and at its other end to a slider 24. The slider 24, also commonly referred to as a head or a read/write head, typically includes an inductive write element with a sensor read element.
As the motor 14 rotates the magnetic disk 16, as indicated by the arrow R, an air bearing is formed under the slider 24 allowing it to “fly” above the magnetic disk 16. Discrete units of magnetic data, known as “bits,” are typically arranged sequentially in multiple concentric rings, or “tracks,” on the surface of the magnetic disk 16. Data can be written to and/or read from essentially any portion of the magnetic disk 16 as the voice-coil actuator 18 causes the slider 24 to pivot in a short arc, as indicated by the arrows P, over the surface of the spinning magnetic disk 16. The design and manufacture of magnetic disk data storage systems is well known to those skilled in the art.
Reducing the distance between the slider 24 and the spinning disk 16, commonly known as the “fly height,” is desirable in magnetic disk drive systems 10 as bringing the magnetic medium closer to the inductive write element and sensor read element improves signal strength and allows for increased areal densities. However, as the fly height is pushed to lower values, the effects of contamination at the head-disk interface become more pronounced. Specifically, debris may be collected over time on the air bearing surface of the slider 24 and which may ultimately cause the slider 24 to crash into the magnetic disk 16 causing the disk drive system 10 to fail. Consequently, reducing contamination within the sealed enclosure 12 is a continuing priority within the disk drive industry.
One strategy that has been used to reduce the debris that collects on slider 24 is to focus on the tribology at the head-disk interface to reduce the amount of contact between the slider 24 and the disk 16 when the system 10 is started and stopped. Traditionally, when a system 10 was shut down the slider 24 was parked on a track at the inner diameter (ID) of the disk 16 commonly known as a landing zone. There the slider 24 would rest in contact with the surface of the disk 16 until the disk was spun again, at which point the air bearing would form and the slider 24 would lift back off of the surface. Unfortunately, the friction and wear that occurred in these systems at the head-disk interface, even with improved lubricants, created unacceptable amounts of debris on the slider 24 to allow for still lower fly heights. In order to reduce friction and wear at the head-disk interface so as to reduce debris accumulation, the landing zone was improved by making it textured, often with a pattern of bumps, in order to reduce the contact area between the slider 24 and the disk 16, among other reasons.
Textured landing zones proved effective to a point; however, the need to fly the slider 24 still lower, with the inevitable need to reduce contamination further, led to the development of techniques whereby the slider 24 is held off of the surface of the disk 16 when not in use. Such techniques seek to avoid any contact between the slider 24 and disk 16 at all. However, simply lifting the slider 24 higher off of the surface of the disk 16 is not sufficient because a system 10 in a portable computer system is subject to shock that can cause the slider 24 to slap into the disk 16. Therefore, a technique used in the prior art to securely park the slider 24 away from the surface of the disk 16, as shown in FIG. 2, is to employ a small ramp 30 placed proximate to the outer diameter (OD) of the disk 16 and a tab 32 attached to the slider 24. As the voice-coil actuator 18 causes the slider 24 to move toward the extreme OD the tab 32 rides up on the ramp 30 and lifts the slider 24 away from the surface. The slider 24 is pushed still further along the ramp 30 past the OD of the disk 16 to be parked on a flat or slightly indented portion on the ramp 30.
FIGS. 3 and 4 serve to better illustrate the relationships between the components of ramp systems of the prior art. FIG. 3 shows an elevational view, taken along the line 3—3 in FIG. 2, of a slider 24 of the prior art suspended beneath a load beam 20 by a flexure 22. Attached to the end of the load beam 20 is a tab 32 intended to move in sliding contact with a ramp 30 for loading and unloading the slider 24. Although shown as attached to the end of the load beam 20, it should be noted that the tab 32 is typically formed as an integral part of the load beam 20.
FIG. 4 shows an elevational view, taken along the line 4—4 of FIG. 2, of the ramp 30 relative to the tab 32, read slider 24, and the disk 16, when the slider 24 is flying and the tab 32 is disengaged from the ramp 30. For clarity, the load beam 20 and the flexure 22 are not shown. The tab 32 has a rounded bottom surface to reduce the contact area with the ramp 30 when the two are in sliding contact. Arrows in FIG. 4 indicate the directions of motion of the load beam 20 for both loading and unloading.
One problem with a ramp 30 of this design is that the tab 32 is in sliding contact with the ramp 30 each time the system 10 is started or stopped. The sliding contact produces wear contamination that can be transferred to the disk 16 to be picked up by the air bearing surface of the slider 24. The wear may be reduced by shaping the tab 32 so that the surface that contacts the ramp 30 is convex and by employing a lubricant. Although the amount of wear debris formed in this way is less significant compared to that which is generated with textured landing zones, nevertheless it may interfere with the aerodynamics of the slider 24 at very low fly heights and lead to crashes.
Another problem encountered with ramps 30 is that the slider 24 is not entirely parallel to the surface of the disk 16. Rather, the leading edge of the slider 24, the one facing into the direction of the rotation of the disk 16, is higher than the trailing edge of the slider 24 to provide lift. Viewed another way, the pitch on the slider 24 causes the trailing edge to be closer to the surface. Similarly, since the air flow under the side of the slider 24 nearest the OD is always greater than under the side nearest the ID, the slider 24 may have some roll such that the ID edge of the slider is lower than the OD edge. Consequently, the corner of the slider 24 on the ID side of the trailing edge is commonly closest to the surface. As a slider 24 is loaded over a disk 16 the tab 32 slides down the ramp 30 until the lift experienced by the slider 24 is sufficient to cause the slider to fly.
What is desired, therefore, is a way to park the slider 24 on a ramp 30 while minimizing as much as possible the wear between the tab 32 and the ramp 30. It is further desired to provide a smoother transition during loading and unloading.